Answer:
76454
Step-by-step explanation:
Sequence : 14,56,224, ..14(4^(n-1)
where n=term number.
First term: 14*(4^(1-1)) = 14*(4^0) = 14
Second term: 14*(4^(2-1))=14*4 = 56
Third term: 14*(4^(3-1))=14*16 = 224
...
7th term: 14*(4^(7-1)) = 14*(4^6)
Sum of the first 7 terms
= 14*(4^0+4^1+4^2+4^3+4^4+4^5+4^6)
= 14(4^7-1)/(4-1)
= 14(4^7-1)/3
= 76454
